TY - JOUR
T1 - Effect of causality constraints on Bayesian analyses of heavy-ion collisions
AU - Domingues, Thiago S.
AU - Krupczak, Renata
AU - Noronha, Jorge
AU - Da Silva, Tiago Nunes
AU - Paquet, Jean François
AU - Luzum, Matthew
N1 - Publisher Copyright:
© 2024 American Physical Society.
PY - 2024/12
Y1 - 2024/12
N2 - There have long been questions about the limits to the validity of relativistic fluid dynamics and whether it is being used outside its regime of validity in modern simulations of relativistic heavy-ion collisions. An important new tool for answering this question is a causality analysis in the nonlinear regime-if the solutions of the evolution equations do not respect relativistic causality, then they are not a faithful representation of the underlying relativistic theory (in this case, quantum chromodynamics). Using this nonlinear criterion, it has recently been shown that hydrodynamics is indeed being used outside its regime of validity in simulations, at least sometimes. Here we explore the phenomenological implications, particularly the quantitative effects of demanding limits on acausality in modern Bayesian parameter estimation. We find that, while typically only a small fraction of the system's energy is initially in an acausal regime, placing strict limits on the allowed energy fraction significantly changes the preferred properties of the initial condition, which in turn alters the extracted medium properties such as bulk viscosity, where large values are no longer favored. These findings highlight the importance of developing better theoretical descriptions of the early-Time, out-of-equilibrium dynamics of relativistic heavy-ion collisions.
AB - There have long been questions about the limits to the validity of relativistic fluid dynamics and whether it is being used outside its regime of validity in modern simulations of relativistic heavy-ion collisions. An important new tool for answering this question is a causality analysis in the nonlinear regime-if the solutions of the evolution equations do not respect relativistic causality, then they are not a faithful representation of the underlying relativistic theory (in this case, quantum chromodynamics). Using this nonlinear criterion, it has recently been shown that hydrodynamics is indeed being used outside its regime of validity in simulations, at least sometimes. Here we explore the phenomenological implications, particularly the quantitative effects of demanding limits on acausality in modern Bayesian parameter estimation. We find that, while typically only a small fraction of the system's energy is initially in an acausal regime, placing strict limits on the allowed energy fraction significantly changes the preferred properties of the initial condition, which in turn alters the extracted medium properties such as bulk viscosity, where large values are no longer favored. These findings highlight the importance of developing better theoretical descriptions of the early-Time, out-of-equilibrium dynamics of relativistic heavy-ion collisions.
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U2 - 10.1103/PhysRevC.110.064904
DO - 10.1103/PhysRevC.110.064904
M3 - Article
AN - SCOPUS:85211486795
SN - 2469-9985
VL - 110
JO - Physical Review C
JF - Physical Review C
IS - 6
M1 - 064904
ER -